The Experimental Studies Of Non-thermal Plasma Sterilization

Owing to its abundance of active radicals, charge particles and the UV radiation, which are potential sterilizing agents, the low temperature plasma is a promising new sterilization technology with safe, rapid, simple and no hazard remnant. In recent years , the study of the plasma sterilization is an interesting topic in the low temperature plasma research.In the thesis, the experimental study of the plasma sterilization by using dielectric barrier discharges (DBD) has been conducted. The culture and the test of microorganism are described. A new DBD discharge device using in experiments is designed and setup. The discharge configuration and electric parameters are measurement. The sterilization effect on bacteria of DBD plasma is studied in different conditions primary. The influence of the type of discharge gas, the type of bacteria on the sterilization effect has been investigated. The bacteria inactive effect are analyzed by plate count method and the survival curves are presented, the D value which characterized the sterilization effect are given. The mechanism of the plasma sterilization and the elements affect the sterilization are explored.The experimental results indicate that the DBD plasmas can destroy bacteria effectively. Escherichia Coli is killed in O₂ plasma only in tens of seconds. So sterilization of effect plasma technology is higher than that of conventional one. The presence of the multi D value in survive cures imply that more than one inactivation mechanisms contribute simultaneously to the sterilization process.It is found that sterilization effect in O₂ plasma is great better than that of Ar and N₂ plasmas. Oxygen is a strong active material, the abundance of active species in O₂ plasma play a significant role during sterilization. It is convinced that the active species contribute more effect than that of UV radiation in the plasma sterilization.The experiments of plasma inactive effect for different type microorganism shows that the plasma sterilization is more effective in Escherichia coli (Gram negative bacteria) than that of Staphylococcus aureus (Gram positive bacteria).The reason cause this maybe relate to difference cytoarchitecture in Gram negative and Gram positive bacteria. The thick and stout cell wall let the gram positive bacteria can bear a longer plasma etching, and so need more to time destroy it.The experiments on the effect of the support medium on the plasma sterilization are conducted and it is found the inactive effect is sensitive to the support materials. The surface roughness and the heat absorb and heat conductive properties of the carrier will affect the sterilization effect. Among the glass, ceramic and PP plastic, the PP plastic carrier has the weakest sterilization effect. The sterilization effect on glass is better than that of other twos if the exposure time in plasma is not longer enough for heating the support materials.